Hello, I have a 1988 300e that i have in the shop trying to resolve an AC problem. I have had the car for several years and drove it without the AC, however I have now decided to pass the car on to my son and need to get the AC fixed. The car is at the shop and the mechanic is telling me that the Compressor is fine but there is no power getting to the AC by the normal means. Are there any suggestions on what I might be dealing with, and how I should troubleshoot to resolve the issue. I am also having problems with the ignition switch sticking when turned to the on and off position. However the AC problems has been a problem before the sticking switch. I wanted to mention this just in case.

Thanks in advance for any assistance anyone can provide.

bigchat1

1988 300e
2001 E320 Sport
1976 230 - Down with bad engine

 

It would seem reasonable that a fuse has blown, or bad A/C relay behind the fusebox would be suspect. If you need a diagram of the relays or need to know which relay it is, I'll look it up for ya.

 

Regarding the ignition switch, I had the same problem. I went to the dealer and ordered a new key. Works great. It's probably a good idea to replace your keys every 10 years or so to prevent damage and excessive wear to the ignition lock cylinder.

Regarding the AC, if the charge is low there will be no power to the compressor because the low pressure switch contacts will be open. If there is no power to the low pressure switch then that is another problem. That could be an open low temp cutout switch, or a problem with the HVAC controls.

 

My Bad...The service CD says that the A/C compressor control unit is located on the right side of the firewall, near the battery.

 

Thanks for all the replys, I will check any an all fuses and any help with the diagram would be helpful

In reference to the open low temp cutout switch, where is that located and what is the best way to troubleshoot to determine if it is bad The HVAC, i have heard it before, but can not remember what the acornym stands for.

 

IF the ac was charged could it be that the lower Pressure switch is bad? Also what is the best way to eliminate that it is the control unit in the dash where the climate control dial is and the ac on/off button is. I quess that i really need to locate a diagram and troubleshoot it with a ohm meter.

 

Jumper the low pressure switch. The compressor should cycle with the center button pressed, or all buttons out (auto mode).

 

Thnaks so much for your help. I will try this, let me know if anything else comes to mind. thanks to all, and Please continue to post if you have any ideas of what i might be dealing with

 

This may not help you much, cause it looks like you need to have the whole A/C system checked over, but here's one location:

 

How does the shop know the compressor is fine if there is no power to it? Plus why can't they figure out why it has no power? Find another shop that knows what they are doing. When I got my old 1988 300E at a garage sale the AC wasn't working. After troubleshooting here is what I found:

Compressor clutch failed and went to ground. Ohms to ground = zero. This caused an excessive current draw on the clutch control circuit (CCC) which burned up a resistor on the board inside the KLIMA relay. The KLIMA relay controls the AC compressor clutch and is located near the battery. I took the KLIMA relay apart and could see the burned resistor. Bought a used KLIMA relay, rebuilt compressor, and a drier on Ebay. Installed all and added an inline fuse in the wire from the KLIMA relay to the AC clutch. (Incredibly enough these overengineered cars DO NOT have a fuse protecting this expensive relay....if the clutch grounds it will toast the KLIMA), recharged the system and it has worked fine for 3 years....also I have never blown the inline fuse I installed.

I got the car cheap because w/o AC the dark red interior made it UNBEARABLE to drive in Atlanta during the summer.